I do not know the correct name for the spouts that return the water into the pool. I have four of these spouts; one of them has been expelling air bubbles during the time the filter is running. My idea is that the sand in the filter needs cleaning. By the way, I have only been at this home for about 6 months - don't know the maintenance history on the pool. Any suggestions? Thanks![/b]

Air in the return line implies that the pump is sucking air into the system. It is unlikely to be due to the filter which is plumbed AFTER the pump.

Very often the pump filter basket cover is not seated correctly or the o-ring is worn. Turn off the pump and try to find a slow leak or drip at the pump or the piping leading up to it on the suction (skimmer) side. An area of dampness or a slow drip will show where the pump is sucking air from.